An unjustly forgotten American novelist is James Branch Cabell. My favorite of his books is probably The High Place, but that is not on Gutenberg.org. His most famous book is Jurgen, because it was banned in Boston for indecency, which catapulted Cabell from obscurity to fame, however brief. Highly recommended for married men over the age of 25*, who are least likely to be corrupted by it.
How about something from JP Donleavy? I’ll concede there’s a sameyness about his output, to the extent that I suspect many will say that their favourite Donleavy book is the first one they read - in my case The Onion Eaters (YMMV).
I don’t know what the unwritten date cut-off is. Is American Psycho by Bret Easton Ellis to recent?
I’m a fan of William Least Heat-Moon; Blue Highways is his classic, and I’m currently reading River Horse, his tale of crossing America east to west by boat.
And, as I usually do in these kind of threads, I highly recommend anything by Tony Horwitz, Confederates In The Attic and A Voyage Long And Strange, to name a couple.